Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
The positioning of the end effector is constrained by the trocar. Generally, these endoscopic surgical instruments include a long shaft between the end effector and a handle portion manipulated by the clinician. This long shaft enables insertion to a desired depth and rotation about the longitudinal axis of the shaft, thereby positioning the end effector to a degree. With judicious placement of the trocar and use of graspers, for instance, through another trocar, often this amount of positioning is sufficient. Surgical stapling and severing instruments, such as described in U.S. Pat. No. 5,465,895, are an example of an endoscopic surgical instrument that successfully positions an end effector by insertion and rotation.
More recently, U.S. patent Ser. No. 10/443,617, “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM” to Shelton IV et al., filed on 20 May 2003, which is hereby incorporated by reference in its entirety, describes an improved “E-beam” firing bar for severing tissue and actuating staples. Some of the additional advantages include the ability to affirmatively space the jaws of the end effector, or more specifically a staple applying assembly, even if slightly too much or too little tissue is clamped for optimal staple formation. Moreover, the E-beam firing bar engages the end effector and staple cartridge in a way that enables several beneficial lockouts to be incorporated.
These surgical stapling and severing instruments include a shaft having a frame that guides a firing bar that performs the firing. A closure tube slides overtop of the frame and firing bar to effect closure of the jaws of the staple applying assembly. Thereby, a separate closure and firing capability are provided that allow increased clinical flexibility. The surgeon may repeatedly close and reposition tissue until satisfied with the placement.
Depending upon the nature of the operation, it may be desirable to further adjust the positioning of the end effector of an endoscopic surgical instrument. In particular, it is often desirable to orient the end effector at an axis transverse to the longitudinal axis of the shaft of the instrument. The transverse movement of the end effector relative to the instrument shaft is conventionally referred to as “articulation”. This is typically accomplished by a pivot (or articulation) joint being placed in the extended shaft just proximal to the staple applying assembly. This allows the surgeon to articulate the staple applying assembly remotely to either side for better surgical placement of the staple lines and easier tissue manipulation and orientation. This articulated positioning permits the clinician to more easily engage tissue in some instances, such as behind an organ. In addition, articulated positioning advantageously allows an endoscope to be positioned behind the end effector without being blocked by the instrument shaft.
Approaches to articulating a surgical instrument tend to be complicated by several conflicting design goals. The articulation joint, as part of the elongate shaft, should be as small a diameter as possible to minimize the size of the required surgical opening and thus enhance post-operative recovery. However, a firing member that translates across the articulation joint needs to be strong enough to successfully transfer firing loads yet flexible enough to not significantly increase the force to fire through an articulated shaft. Moreover, a flexible firing member should not cause misfiring due to a “blow out” in the articulated shaft.
Recently, in U.S. Patent Application 2005/0006429 A1, Ser. No. 10/615,971, entitled “SURGICAL STAPLING INSTRUMENT HAVING ARTICULATION JOINT SUPPORT PLATES FOR SUPPORTING A FIRING BAR” to Wales, et al., filed 9 Jul. 2003, and in U.S. Patent Application 2005/0165415 A1, Ser. No. 11/083,740, entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING AN ELECTROACTIVE POLYMER ACTUATED FIRING BAR TRACK THROUGH AN ARTICULATION JOINT” to Wales, filed 18 Mar. 2004, both of which are hereby incorporated by reference in their entirety, articulation joints with a pair of flexible supports are described that flank the firing bar to prevent blow out.
While such support plates are an advancement in articulating shafts that support a firing bar (e.g., surgical staplers), it would be desirable to have another approach that requires a low articulation force and provides good structural support to the articulation joint. Consequently, a significant need exists for an improved surgical stapling and severing instrument having an articulating shaft that supports a firing bar.